Power change-over mechanism of a vehicle for industrial machinery

ABSTRACT

A power change-over mechanism of a vehicle for industrial machinery including a spool divided into two members: an outer peripheral side member having splines freely meshed with splines of high-speed and low-speed gears and an inner peripheral side member having a spline freely meshed with splines of first and second driving shafts, an inner peripheral sub-spline constantly meshing with the first driving shaft being further formed on the outer peripheral side member, the outer peripheral side member being clearance fitted onto an outer periphery of the inner peripheral side member, and the inner and outer peripheral side members being connected relatively movable with respect to each other in the axial direction through a damper means.

BACKGROUND OF THE INVENTION

1. Field of Industrial Usefulness

This invention relates to a power change-over mechanism of a vehicle forindustrial machinery, which permits free change-over between four-wheeldrive and two-wheel drive.

2. Prior Art

In FIG. 1 showing a conventional embodiment, a first driving shaft 1 fordriving a rear wheel and a second driving shaft 2 for driving a frontwheel are both aligned on the same axis center, and at the same timethey have outward splines 3, 4 respectively. A high-speed gear 5 and alow-speed gear 6 fit onto the first and second driving shafts 1, 2through bearings 7, 7a, and at the same time they have inward splines 8,9 respectively. An annular power change-over spool (spline joint) 10 hasan inward spline 11 and a pair of outward splines 13, 14 and at the sametime it provides an annular groove 16 for engagement with a shift forkand spline fits onto the first driving shaft 1 freely slidingly operablyin the axial direction.

In case of the four-wheel drive, the spool 10 is shifted forward tointerconnect the low-speed gear 6 through the spool 10 to the first andsecond shafts, 1,2. Namely, a power transmitted from an engine through atransmission to the low-speed gear 6 is transmitted through the splines9, 14 to the spool 10, and further transmitted from the spool 10 to thefirst driving shaft 1 through means of the splines 11, 3 and to thesecond driving shaft 2 through means of the splines 11, 4.

In case of the two-wheel drive, the spool 19 is shifted rearward tointerconnect the high-speed gear 5 through the spool 10 to the firstdriving shaft 1. Namely, the power transmitted from the engine throughthe transmission to the high-speed gear 5 is transmitted through thesplines 8, 13 to the spool 10, and further transmitted from the spool 10to the first driving shaft 1 through means of the splines 11, 3 to drivethe rear wheel.

However, in case when the power change-over mechanism is composed of thepower change-over annular spool 10 as a member, the followingdisadvantages will arise at the time of change-over. Generally, in caseof power change-over, a power from an engine has previously been cut offby means of a clutch etc. and the change-over operation is done with avehicle stopped. However, in case of change-over from the two-wheeldrive to the four-wheel drive, meshing of gears is under fixed conditionbecause of the driving shaft 1 being interconnected to the rear wheeland the driving shaft 2 being interconnected to the front wheel, so thatthe spline 11 of the spool 10 would not mesh with spline 4 of thedriving shaft 2 to make the change-over from the two-wheel drive intothe four-wheel drive impossible.

Further, under a normal four-wheel drive operations, a torsion will beproduced between the driving shafts 1, 2 due to slippage of wheel andlarge contact forces will be generated between the spline 3 of thedriving shaft 1 and the spline 11 of the spool 10 and between the spline4 of the driving shaft 2 and the spline 12 of the spool 10, so that thespool 10 would not slide to make the change-over from the four-wheeldrive into the two-wheel drive impossible. For this reason, achange-over from a high-speed into a low-speed or a change-over from alow-speed into a high-speed will naturally become impossible.

The applicant of this invention proposed in the application (Japan Ser.No. S58-108286: U.S. Ser. No. 621,318 now U.S. Pat. No. 4,553,623), as ameans to improved the above disadvantage, the means in which thechange-over spool was divided into two: the outer peripheral side memberand the inner peripheral side member, and the both members were splinefitted axially slidingly each other through the damper. However, thephenomenon of change-over from the four-wheel drive to the two-wheeldrive being impossible was not completely dissolved because a power wasdirectly transmitted between the outer peripheral side member and theinner peripheral side member when they were spline connected.

Object of the Invention

An object of this invention is to enable the disadvantage of theconventional embodiment shown in FIG. 1 to be more perfectly dissolvedby improving said mechanism of application No. S58-180286, i.e. tosimply and securely enable the change-over between four-wheel drive andtwo-wheel drive and the change-over between high-speed and low-speed byoperating one set of spool only once even under a condition where thedriving shafts of front and rear wheels do not mesh each other due todeviation of spline phase thereof, or under a condition where a torsionis produced between the driving shafts of the front and rear wheels.

In order to accomplish the above object, in a power change-overmechanism of this invention, a spool is divided into two: an outerperipheral side member having splines freely meshed with splines ofhigh-speed and low-speed gears and an inner peripheral side memberhaving a spline freely meshed with splines of said driving shafts, aninner peripheral sub-spline constantly meshing with the first drivingshaft is further formed on the outer peripheral member, the outerperipheral member is clearance fitted onto an outer periphery of theinner peripheral member, and the outer and inner peripheral members arerelatively movably connected in the axial direction through a dampermeans.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical sectional view of a conventional embodiment.

FIG. 2 is a vertical sectional view of a first embodiment of thisinvention.

FIG. 3 is a vertical sectional view of a second embodiment of thisinvention.

FIG. 4 is a sectional view taken on a line IV--IV of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment 1

FIG. 2 is the vertical sectional view of the first embodiment an upperhalf of which shows a four-wheel drive state and a lower half of whichshows a neutral state, and a component corresponding to that of FIG. 1is attached with the same number as FIG. 1. In this FIG. 2, first andsecond driving shafts 1, 2 are aligned on the same axis center throughan aligning bearing metal 19, the first driving shaft 1 isinterconnected, for example, to a rear wheel at a rear side and thesecond drive shaft 2 is interconnected to a front wheel at a front side.A high-speed gear 5 fits freely rotatably onto the first driving shaft 1through a bearing 7, a low-speed gear 6 fits freely rotatably onto thesecond driving shaft 2 through a bearing 7a, the both gears 5, 6 meshwith appropriate gears of a transmission (not shown) respectively, thusa power being transmitted from an engine through a clutch etc.Naturally, the high-speed gear 5 rotates at a higher speed than that ofthe low-speed gear 6.

Outward splines 3, 4 are formed on the first and second driving shafts1, 2 respectively, and inward splines 8, 9 are formed on bosses of theboth gears 5, 6 respectively. The spline 8 of the high-speed gear 5faces at the spline 3 of the first driving shaft 1 with a space lefttherebetween and the spline 9 of the low-speed gear 6 faces at thespline 4 of the second driving shaft 2 with a space left therebetween.

A power change-over annular spool (spline joint) 10 disposed between theboth gears 5, 6 is divided into two: an outer peripheral side member 20and an inner peripheral side member 21, and the outer peripheral sidemember 20 fits onto an outer periphery of the inner peripheral sidemember 21 axially movable with respect to each other and with an annularclearance d provided therebetween. Namely, the spool is so deviced thata power is not transmitted directly from the outer peripheral sidemember 20 to the inner peripheral side member 21.

Splines 13, 14 freely meshed with the splines 8, 9 of the gears 5, 6 areformed on an outer peripheral surface of the outer peripheral sidemember 20, and an inner peripheral sub-spline 22 constantly meshing withthe spline 3 of the first driving shaft 1 is formed at a rear endportion of the outer peripheral side member 20. An annular spring washer23 fits in an inner peripheral side of a front end portion of the outerperipheral side member 20, and is stopped by a snap ring. An annulargroove 16 is formed on an outer periphery of the outer peripheral sidemember 20, and a shift fork 15 engages with the annular groove 16.

The inner peripheral side member 21 is disposed at an axially centralpart between the sub-spline 22 and the spring washer 23. A spline 11constantly meshing with the spline 3 of the first driving shaft 1 isformed on an inner peripheral surface of the inner peripheral sidemember 21, and this spline 11 is freely meshed with the spline 4 of thesecond driving shaft 2.

A first coil spring 25 urging the inner peripheral side member 21forward relatively to the outer peripheral side member 20 and a secondcoil spring 26 urging the inner peripheral side member backwardrelatively thereto are provided as a damper means. Namely, anopened-backward first spring receiving recession 27 and anopened-forward second spring receiving recession 28 are formed on theinner peripheral side member 21, the first spring 25 is insertedprojectingly backward into the first spring receiving recession 27, andthe second spring 26 is inserted projectingly forward into the secondspring receiving recession 28. A rear end of the first spring 25 presseson a front face of a barrel 22a of the sub-spline 22, and a front end ofthe second spring 26 presses on a rear face of the washer 23. The innerperipheral side member 21 is held at an axially central position betweenthe washer 23 and the sub-spline 22. Incidentally, the first spring 25is disposed, for example, on three places spaced equally in thecircumferential direction, and the second spring 26 is also disposed onthree places.

Function of the Invention

As illustrated in the upper half of FIG. 2, when the entire spool 10 ismoved toward the front side, the front side spline 14 of the outerperipheral side member 20 fits into the spline 9 of the low-speed gear 6and at the same time the spline 11 of the inner peripheral side member21 fits onto the spline 4 of the second driving shaft 2, thus alow-speed four-wheel drive state is created. A power transmitting pathat this moment is explained as follows: A power is transmitted from thelow-speed gear 6 through the splines 9 & 14, the outer peripheral sidemember 20 and the splines 22 & 3 to the first driving shaft 1. Further,the power is transmitted from the first driving shaft 1 through thesplines 3 & 11, the inner peripheral side member 21 and the splines 11 &4 to the second driving shaft 2, thereby the both shafts 1, 2 rotate ata low speed.

When the entire spool 10 is moved from its neutral position is shown bythe lower half of FIG. 2 to the rear side, the rear side outerperipheral spline 13 of the outer peripheral side member 20 fits intothe spline 8 of the high-speed gear 5, the spline 11 of the innerperipheral side member 21 disengages from the spline 4 of the seconddriving shaft 2, thus a high-speed two-wheel drive state in which onlythe first driving shaft 1 is rotating is created. A power transmittingpath at this moment is explained as follows: A power is transmitted fromthe high-speed gear 5 through the splines 8 & 13, the outer peripheralside member 20 and the splines 22 & 3 to the first driving shaft 1 only.

In case of stopping under the two-wheel drive state, when a phasedifference is produced between the spline 11 of the spool 10 and thespline 4 of the second driving shaft 2, change-over from the two-wheeldrive to the four-wheel drive is performed as follows: When the spool 10is moved forward from the neutral position shown by the lower half ofFIG. 2, the spline 14 of the outer peripheral side member 20 fits intothe spline 9 of the low-speed gear 6, but the spline 11 of the innerperipheral side member 21 only contacts with a rear end of the spline 4of the driving shaft 2 but does not fit with it, thereby the firstspring becomes compressed.

However, at the moment when phases of the both splines 4 & 11 coinsideafter a vehicle starts moving, the spline 11 of the inner peripheralside member 21 is engaged with the spline 4 of the driving shaft 2 by anelastic force (restoring force) of the first spring 25, thus thefour-wheel drive state is automatically created.

In case of stopping under the four-wheel drive state, when a torsion isproduced between the driving shafts 1 & 2 due to slippage of wheel etc.to cause a large pressing force between the spline 3 of the firstdriving shaft 1 and the spline 11 of the spool 10 or a large pressingforce between the spline 4 of the second driving shaft 2 and the spline11 of the spool 10, change-over from the four-wheel drive to thetwo-wheel drive is performed as follows: When the driving mode ischanged from the low-speed four-wheel drive position (the position shownby the upper half of FIG. 2) to the high-speed two-wheel drive positionin case of a torsion produced between the driving shafts 1 & 2, only theouter peripheral side member 20 moves backward against the second springto create the high-speed four-wheel drive first of all. In this instancethe inner peripheral side member 21 is locked by the splines 3, 4 of theboth shafts 1, 2, however, no torque is transmitted directly between theboth members 20, 21 because the outer peripheal side member 20 isclearance fitted onto the inner peripheal side member 21, so that theouter peripheal side member 20 can be moved smoothly backward inrelation to the inner peripheral side member 21. And, at the moment whena vehicle load of the second drivng shaft 2 side instantaneously becomeszero aftr the vehicle starts running from the instantaneous high-speedfour-wheel drive state, the inner peripheral side member 21 is movedbackward by an elastic force of the second spring 26, thus the drivingmode is automatically changed to the hgih-speed two-wheel drive state.

Embodiment 2

FIG. 3 shows an embodiment using one kind of coil spring 29 as thedamper means. Namely, in FIG. 3, a spring receiving notch 30 is formedon an inner peripheral surface of the outer peripheral side member 20, aspring receiving notch 31 corresponding to said notch 30 is formed on anouter peripheral surface of the inner peripheral side member 21, and thespring 29 is compressedly installed in a cylindrical space formed by theboth notches 30, 31 expansively in its axial direction. A front end ofthe spring 29 is stopped by large dia. and small-dia. annular holdingplates 33, 34 through a spring washer 32, and a rear end of the spring29 is stopped by a small-dia. annular holding plate 35 and a shoulderedpat of the outer peripheral side member 20 through a spring wsher 36.The large-dia. holding plate 33 is fixed axially immovably to an innerperipheral surface of the outer peripheral side member 20 by means of asnap ring etc., and the small-dia. holding plates 34, 35 are fixedaxially immovably to an outer peripheral surface of the inner peripheralside member 21 by means of a snap ring. The spring 29 is provided, forexample, at four places equally spaced in the circumferential directionas shown by FIG. 4 for example.

Incidentally, the spring washers 32, 36 are disposed in the notches 30,31 with circumferential plays provided between them, thereby the outerperipheral side member 20 can be slightly rotated relatively to theinner peripheral side member 21.

In FIG. 3 and FIG. 4, a component corresponding to that of FIG. 2 isattached with same member as FIG. 2.

Function of Invention

Samely with the case of said first embodiment, the spring 29 iscompressed when the outer peripheral side member 20 moves in eitherforward or backward direction relatively to the inner peripheral sidemember 21. Namely, the spring 29 is adapted to serve as both the firstand second springs 25, 26 of FIG. 2.

Another Embodiment

(1) The first and second springs 25, 26 of FIG. 2 may be disposedatternatively each other in the circumferential direction withoutaligning them on the same radial line.

(2) The first driving shaft may be used for driving a front wheel andthe second driving shaft may be used for driving a rear wheel. Namely, atwo-front-wheel drive may be employed.

(3) A rubber-type elastic body or an air-spring may be used as thedamper means.

Effect of the Invention

The annular power change-over spool 10 is divided into two: the outerperipheral side member 20 having the splines 13, 14 freely meshed withthe splines 8, 9 of the high-speed gear 5 and lhe low-speed gear 6 andthe inner peripheral side member 21 having the spline 11 freely meshedwith the splines 3, 4 of the first and second driving shafts 1, 2; theouter peripheral side member 20 is clearance fitted onto the innerperipheral side member 21; the sub-spline 22 constantly meshing with thespline 3 of the first driving shaft 1 is formed on the outer peripheralside member 20; and the both members 20, 21 are adapted to be relativelymovable each other in the axial direction through the damper means; sothat the following effects are obtainable.

(1) Even when the vehicle is stopping under the condition where thesplines 3, 4 of the driving shafts 1, 2 for front and rear wheels do notmesh each other through the spool 10 due to the phase differenceproduced therebetween or under the condition where the load is applied,the only one-time operation of the spool 10 surely enables thechange-over between high-speed and low-speed when the vehicle isstopping, and automatically enables the change-over between two-wheeldrive and four-wheel drive by the restoring force of the damper meanswhen the vehicle starts moving. Namely, the change-over operation by thespool 10 can be simply and surely performed and the troubles such as thechange-over beconing impossible, the gear noise etc. can be dissolved.

(2) The power is not directly transmitted between the both members 20,21 by clearance fitting the outer peripheral side member 20 onto theinner peripheral side member 21, so that the outer peripheral sidemember 20 can be moved always smoothly in the axial direction relativelyto the inner peripheral side member 21. Namely, the troubles such as thechange-over being impossible etc. can be dissolved much more surely.

(3) The change-overs between high-speed and low-speed and betweentwo-wheel drive and four-wheel drive become possible by connecting, forexample, one shift fork 15 to the spool 10 assembled as one unit, sothat a volume of the mechanism can be minimized and its manufacturingcost can be decreased.

What is claimed is:
 1. A power changeover mechanism of a vehicle forindustrial machinery comprising:a. a first driving shaft and ahigh-speed gear mounted for rotation thereon; b. a second driving shaftdisposed in coaxial arrangement with said first driving shaft and havinga low speed gear mounted for rotation thereon; c. splines formed in bothsaid shafts and both said gears; d. a power change-over annular spooldisposed between said gears freely slidingly operable in an axialdirection from a two-wheel drive position to a four-wheel driveposition; e. said spool being divided into two members; an outerperipheral member having a cylindrical portion with exterior splines forfreely meshing with said gears and a radially inwardly extending flangeat one end of said cylindrical portion with an interior sub-splineconstantly meshing with the spline of the first driving shaft andadapted for axial movement between said two-wheel drive position andsaid four-wheel drive position; f. said outer peripheral member beingdisposed around an internal peripheral side member with an annularclearance between said members; g. said outer peripheral member alsohaving an annular washer on its inner peripheral surface held againstaxial movement to prevent said washer from moving in a direction awayfrom said flange portion; h. said inner and outer peripheral memberbeing movably connected to each other in the axial direction through adamper means.
 2. A power change-over mechanism of a vehicle forindustrial machinery as set forth in claim 1, in which a first coilspring urging the inner peripheral side member in a forward directionrelatively to the outer peripheral side member and a second coil springurging the former in a backward direction relatively to the latter areprovided as the damper means.
 3. A power change-over mechanism of avehicle for industrial machinery as set forth in claim 2, in which anopened-backward first spring receiving recession and opened-forwardsecond spring receiving recession are formed on the inner peripheralside member, the first spring is inserted in the first spring receivingrcession and a rear end of the first spring is pressed on a rear endbarrel of the outer peripheral side member, and the second spring isinserted in the second spring receiving recession and a front end of thesecond spring is pressed on a front end spring washer of the outerperipheral side member.